Emission-Frequency Separated High Quality Single-Photon Sources Enabled by Phonons

Titelangaben

Cosacchi, Michael ; Ungar, Florian ; Cygorek, Moritz ; Vagov, Alexei ; Axt, Vollrath Martin:
Emission-Frequency Separated High Quality Single-Photon Sources Enabled by Phonons.
In: Physical Review Letters. Bd. 123 (2019) Heft 1 . - 017403.
ISSN 1079-7114
DOI: https://doi.org/10.1103/PhysRevLett.123.017403

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Abstract

We demonstrate theoretically that the single-photon purity of photons emitted from a quantum dot exciton prepared by phonon-assisted off-resonant excitation can be significantly higher in a wide range of parameters than that obtained by resonant preparation for otherwise identical conditions. Despite the off- resonant excitation, the brightness stays on a high level. These surprising findings exploit the fact that the phonon-assisted preparation is a two-step process where phonons first lead to a relaxation between laser- dressed states while high exciton occupations are reached only with a delay to the laser pulse maximum by adiabatically undressing the dot states. Due to this delay, possible subsequent processes, in particular multiphoton excitations, appear at a time when the laser pulse is almost gone. The resulting suppression of reexcitation processes increases the single-photon purity. Due to the spectral separation of the signal photons from the laser frequencies this enables the emission of high quality single photons not disturbed by a laser background while taking advantage of the robustness of the phonon assisted scheme.